Nanda Devi: A Journey to the Last Sanctuary by Hugh Thomson 125pp, Weidenfeld, £18.99

Hugh Thomson's first book was an enthralling account of his search for a lost city close to Machu Picchu in the Peruvian Andes. In choosing India's highest mountain as his second focal point, he has embarked once more on a quest, quite as heroic in its acceptance of hardship and danger. But although many of the gifts he brought to The White Rock are visible once more, others are not, because, paradoxically, the 25,000-ft Himalayan peak has provided him with a much smaller subject.

The greatest strength of the earlier work was his knowledge and understanding and interpretation of the highly sophisticated Inca civilisation. He came across nothing comparable during the relatively short time he spent in the Garhwal, and it shows.

This is the story of an expedition whose object was not to climb one of the most beautiful and intimidating mountains on earth, but simply to reach the bottom of it. The great valley running along its southern wall, the Nanda Devi Sanctuary, which Thomson describes as "a veldt of high grassland, curling around the mountain in a way that managed to be both inviting and grandiose", had been closed to foreigners for many years because of its delicate position on the border with Tibet.

But, as a millennium project, the Indian government allowed a mostly British group of climbers to inspect the area, with a view to limited access in future. Thomson was the least experienced mountaineer in the party: at 40 he was also the youngest, in the company of some very distinguished names. One was George Band, the junior member of the first successful Everest expedition in 1953 and now, at 71, with "the loping, slightly bow-legged gait of a man who has been rolling down from summits all his life". Another was Ian McNaught-Davis, the International Mountaineering and Climbing Federation's president and notable on this occasion for his stunning versatility with a single four-letter word.

A great deal of the narrative surveys past efforts to climb the mountain, which defeated the august membership of the Alpine Club (anxious to conquer the topographical summit of the British Empire) for almost a century: nobody, dammit, could even get to the base of this mountain, so hemmed in was it by natural obstacles. It defeated Hugh Ruttledge three times in the inter-war years before he wrote (to the Times, naturally) that "Nanda Devi imposes on her votaries an admission test as yet beyond their skill and endurance". He thought the Sanctuary alone was more inaccessible than the North Pole.

There's quite a bit about the class-ridden history of major climbing and Thomson's conclusions are not predictable. For all their toffee-nosed exclusivity, the old grandees did esteem mountains as places worth submitting to humbly after honourable engagement. Nanda Devi has always been worshipped in the Garhwal as a manifestation of the Lord Shiva's consort Parvati and has therefore been treated immaculately.

In the 1970s, George Band and the Manchester jobbing builder Joe Brown stopped short of Kangchenjunga's summit because the Buddhists of Sikkim had asked them to. Since then, the hard men have taken over, not giving a stuff for anything but getting to the top and breaking records, leaving all manner of filth in huge quantities behind them.

Thomson has a nose for stories, and the best here is his discovery of the real reason for Nanda Devi's being off limits for so long. The CIA in 1965 decided to instal a nuclear-powered surveillance gadget on her summit, where it could overlook and report on what was going on in Chinese-occupied Tibet. The finest American climbers of their generation were recruited to make this fantasy come true, but unfortunately the thing was buried in a landslide on the way up and its plutonium-238 core will be oozing radioactivity into the adjacent headwaters of the sacred Ganges for anything up to the next 300 years.

Just as chilling (but in a different class) is the tale of 22-year-old Devi Unsoeld, who went to the mountain she'd been named after with her father and her fiancé in 1976, on a special expedition. She became ill and died just below the summit, and at 24,000 feet it was impossible to get her body back down. So the two men "bundled Devi up in her sleeping bag and slipped her over the precipice of the North-east Face as if, in Willi's distraught words, 'committing her body to the deep'." I don't believe I shall forget that distressing image; or the photographs in Hugh Thomson's book that picture the sensational and, yes, holy landscape in which all the events he describes took place.